Hose with corrugated metal tube

ABSTRACT

A hose body of a hose with corrugated metal tube has a corrugated metal tube of innermost layer and outer layer in a radially outer side thereof including inner elastic layer, reinforced layer and outer elastic layer. A socket fitting is swaged onto the hose body at three axially spaced points thereof. The corrugated metal tube is provided with a straight tubular portion so as to extend for minimum 10 mm beyond the last and third swaged point which is located on an most opposite axial or longitudinal side of the socket fitting.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a hose with corrugated metaltube which is suitable for fuel conveying hose for automobiles,refrigerant conveying hose or any other fluid conveying hose, and moreparticularly to a hose with corrugated metal tube includingcharacteristic structure of an axial end portion thereof.

[0002] Typical rubber hoses, for example, made of blended product ofacrylonitrile-butadiene rubber and polyvinyl chloride (NBR/PVC blend)which is excellent in resistance to gasoline permeability, have beenused for conveying fuel for automobiles or the like in view of theirhigh vibration-absorbability, easy assembling or the like. However, forthe purpose of global environment protection, the regulations have beenrecently tighten against permeation of fuel for automobiles or the like,and are anticipated to be further tighten in the future. Further, hosesare demanded to meet the requirements to convey highly permeable fluidsuch as, hydrogen gas used in fuel cells or carbon dioxide (CO₂)refrigerant. Then it is anticipated difficult to satisfy the futurerequirements with hoses made only of organic materials such as rubber orresin.

[0003] Accordingly, it is currently considered to adapt a hose having acorrugated metal tube for inner layer as future hose of low fluidpermeability because such a hose is expected to have an extremely highfluid impermeability.

[0004] As for a hose with corrugated metal tube, such hoses as disclosedin the-following patent documents, 1, 2 and 3 are known.

[0005] In case of these hoses with corrugated metal tube, even ifadapted for hydrogen gas used for fuel cells, a corrugated metal tube inor as an inner layer reduces gas permeation to zero, i.e., completelyeliminates permeation of gas.

[0006] 1. JP, A, 2001-182872

[0007] 2. U.S. Ser. No. 20020007860A1

[0008] 3. JP, U, 51-150511

[0009] And, FIG. 5 shows a hose with corrugated metal tube of this typewhich is invented by the inventors of the present invention and helpfulfor better understanding of the present invention. In FIG. 5, a numeralreference 200 indicates a hose body. The hose body 200 is formedmulti-layered. The multi-layered construction has inner layer includinga corrugated metal tube 202 of innermost layer and outer layer whichcircumscribe a radial outer side of the inner layer and includes innerelastic layer 204, reinforced layer 206 and outer elastic layer 208.

[0010] A numeral reference 210 indicates a socket fitting fitted on anouter periphery of the hose body 200 on an axial or longitudinal endportion, or on one axial or longitudinal end portion of the hose body200. The socket fitting 210 is compressed or swaged radially inwardly atthree axially spaced points P₁, P₂ and P₃ thereof or on a cylindricalportion of the socket fitting 210. And thereby the socket fitting 210and a connecting pipe 212 are fixedly secured to one axial orlongitudinal end portion of the hose body 200 so as to clamp one axialor longitudinal end portion of the hose body 200 therebetween from innerand outer sides thereof.

[0011] Meanwhile, as shown in FIG. 6, in such hose with corrugated metaltube, the corrugated metal tube 202 tends to expand or elongate in anaxial or longitudinal direction when an internal pressure is exertedthereto. Therefore, such hose with corrugated metal tube inherentlyinvolves a fear that when an internal pressure is exerted theretorepeatedly at pulse intervals, the corrugated metal tube 202-overallrepeatedly oscillatingly elongates or expands and contracts in alongitudinal direction, and consequently repeated longitudinaldeformation thereof causes a fatigue crack or crack in the corrugatedmetal tube 202 in any portions thereof. More specifically, it ispredicted that the corrugated metal tube 202 is strongly restrained frommoving on the last swaged point P₃, a stress is likely concentrated in aposition corresponding to the last swaged point P₃, and consequently thecorrugated metal tube 202 is likely subject to fatigue crack or break atthe last swaged point P₃.

[0012] However the inventors of the present invention actually conducteda impulse test or repeated pressurizing test to exert internal pressurerepeatedly to this hose with corrugated metal tube and found the factthat the corrugated metal tube 202 is cracked or broken generally at acertain distance axially away from the last swaged point P₃ of thesocket fitting 210. More specifically, the inventors found the fact thatthe corrugated metal tube 202 is broken about at 7.0 mm axially awayfrom the last swaged point P₃.

[0013] The reason is estimated that a portion of the hose body 200inside of the socket fitting 210 is strongly compressed radiallyinwardly at the last swaged point P₃ when compressing or swaging thesocket fitting 210 radially inwardly, and the compressed portion of thehose body 200 is partly extruded or squeezed out rearwardly (toward theright hand in FIG. 5) as shown by a right-hand arrow in FIG. 5.

[0014] The above are described with reference to a hose for conveyinghydrogen gas used in a fuel cell as example. The similar problems areanticipated in common to any hoses. For example, it may be the case thata hose with corrugated metal tube is employed to convey fuel such asgasoline for the purpose to deal with gasoline or the like permeating toan air or for high temperature and high pressure application due to highoutput power of equipment, where low permeability property is severelyregulated. Also, it may be the case that a hose with corrugated metaltube is employed to particles just like hydrogen and is highlypermeable. Further, it may be any other case that- a hose withcorrugated metal tube is applied in fields under severe regulationsagainst gas permeation.

[0015] It is an object of the present invention to provide a hose withcorrugated metal tube to settle the problems described above.

SUMMARY OF THE INVENTION

[0016] According to the present invention, there is provided a novelhose with corrugated metal tube comprising a hose body having innerlayer including a corrugated metal tube and outer layer includingreinforced (reinforcing) layer, and a socket fitting fitted on the hosebody at one longitudinal or axial end portion thereof and compressed orswaged radially inwardly to be secured thereto. The outer layercircumscribes a radial outer side of the inner layer. The corrugatedmetal tube may be provided with a straight tubular or straight-walledportion extending straight in a longitudinal direction on onelongitudinal or axial end portion of the corrugated metal tube. Thecorrugated metal tube also may be provided with a pre-formed flat andincomplete corrugated portion, for example, extending in a longitudinaldirection thereon. The corrugated metal tube further may be providedwith a straight tubular portion and a pre-formed flat and incompletecorrugated portion thereon. An opposite longitudinal or axial end or arear end of the straight tubular portion or the flat and incompletecorrugated portion is located or extends behind or toward an oppositelongitudinal or axial side from a compressed or swaged point of a mostopposite longitudinal or axial side, or a last compressed or swagedpoint (a last swaged point) of the socket fitting. And, a longitudinalor axial distance between the opposite longitudinal end of the straighttubular portion or the flat and incomplete corrugated portion and thecompressed or swaged point of the most opposite longitudinal side or thelast swaged point of the socket fitting is minimum 10mm. That is, theopposite longitudinal or axial end of the straight tubular portion orthe flat and incomplete corrugated portion is located or extends forminimum 10mm toward an opposite longitudinal or axial side from the lastswaged point. Here, a term “longitudinal” or “axial” is used withrespect to a length or an axis of the hose body, the socket fitting or arelevant member.

[0017] A compressing or swaging rate of the last swaged point for thesocket fitting may be minimum 20%.

[0018] As already described, when a hose with corrugated metal tube isrepeatedly subject to internal pressure, a corrugated metal tube iscracked or broken not at the last swaged point of a socket fitting, butgenerally at a certain distance axially away from the last swaged pointthereof. The reason for this has not been confirmed clearly at present,but is estimated as follows.

[0019] In the hose with corrugated metal tube shown in FIG. 5, asalready explained, a portion of the hose body 200 inside of the socketfitting 210, specifically a portion thereof axially corresponding to thelast swaged point P₃ is strongly compressed radially inwardly and ispartly extruded or squeezed out rearwardly (toward the right hand inFIG. 5) when the socket fitting 210 is compressed or swaged radiallyinwardly.

[0020] At that time, the reinforced (reinforcing) layer 206 is loosen orrelaxed at a portion behind the last swaged point P₃, i.e. a portion ina side of the extruded or squeezed-out part of the outer layer of thehose body 200. In other words, if the reinforced layer 206 is initiallybraided or winded (herein after explained as “braided”) with reinforcingfilament member or members at a neutral angle of about 55 degrees (55°),braid angle (angle of braiding) of the portion on the side of theextruded or squeezed-out part of the outer layer by the swaged socketfitting 210 is changed to be higher than the initial braid angle.

[0021] Braid angle of reinforcing filament member or members in thereinforced layer 206 has a following technical meaning. If braid angleof reinforcing filament member or members in the reinforced layer 206with respect to an axial direction is higher or larger than a neutralangle, the hose including the reinforced layer 206 overall tends toexpand or elongate longitudinally and contract in a radial ordiametrical direction so as to make braid angle of reinforcing filamentmember or members close to or to be a neutral angle when an internalpressure is exerted thereto, as shown in FIG. 7 (a). Here and so forth,it is based on the hypothesis that reinforcing filament member itself orreinforcing filament members themselves do not elongated. And, in “braidangle”, a winding angle is, also included.

[0022] On the contrary, as shown in FIG. 7(c), if braid angle of thereinforcing filament member or members in the reinforced layer 206 islower or smaller than a neutral angle, the hose including reinforcedlayer 206 overall tends to contract in a longitudinal direction andexpand in a radial direction so as to make braid angle thereof close toor to be a neutral angle when an internal pressure is exerted thereto.And, as shown in FIG. 7(b), if braid angle of reinforcing filamentmember or members in the reinforced layer 206 is initially a neutralangle, the reinforcing filament member or members tend to remain at theinitial neutral angle when an internal pressure is exerted thereto. Thatis, the hose overall tends to remain as it is both in diameter andlength.

[0023] Hence, it is estimated that as the reinforced layer 206 providessmall resistance to axial elongation and deformation of the corrugatedmetal tube 202 in the portion behind the last swaged point P₃ if braidangle of the reinforcing filament member or members in the reinforcedlayer 206 becomes high in the portion therebehind as stated above bycompressing or swaging the socket fitting 210 radially inwardly, thecorrugated metal tube 202 more likely expands, elongates, contracts oraxially deforms in the portion therebehind.

[0024] Then the inventors investigated a state of the hose withcorrugated metal tube after repeat pressure test conducted thereto, andconfirmed the reinforced layer 206 actually loosened, relaxed or surgedat the portion behind the last swaged point P₃.

[0025] Further, as shown in FIG. 8, the inventors found at the same timethat the corrugated metal tube 202 is flattened, elongated and deformedaxially, thereby formed actually into incomplete. flat corrugations 214at a portion behind or rearwardly from the last swaged point P₃ undercompressing or swaging pressure of the socket fitting 210, and thecorrugated metal tube 202 is cracked or broken at a border regionbetween the incomplete flat corrugations 214 and the completecorrugations, specifically at a distance corresponding to about twohills or two complete hills from the incomplete flat corrugations 214.

[0026] This phenomenon is estimated to be caused as follows. Theincomplete flat corrugations 214, which was elongated and deformedaxially and thereby was formed, provide high resistance againstelongating and contracting deformation in an axial direction wheninternal pressure is exerted repeatedly. On the other hand, underrepeated internal pressure, the complete corrugations likely elongates,contracts and deforms in an axial direction, further, as stated abovethe reinforced layer 206 provides low resistance against elongatingdeformation in an axial direction of the corrugated metal tube 202 atthe position behind the last swaged point P₃, and thereby the corrugatedmetal tube 202 tends to elongate, contract and deform at the positiontherebehind. Accordingly a stress is likely concentrated around theborder region between the incomplete flat corrugations 214 and thecomplete corrugations specifically. Those factors cooperate each other,and thereby the corrugated metal tube 202 is cracked or broken generallyat a certain distance behind the last swaged point P₃.

[0027] And impulse tests or repeated pressurizing tests are conducted onvarious hoses with corrugated metal tube, and it is proved that in mostof the hoses with corrugated metal tube, corrugated metal tubes arecracked or broken at corrugation hills generally of a certain distancebehind the last swaged point or corrugation hills front or rear of aposition of the certain distance behind the last swaged point,specifically about at 7.0 mm therebehind.

[0028] Here, the incomplete flat corrugations or the flat and incompletecorrugated portion mean corrugations in which a pitch betweencorrugation hills or between corrugation valleys is larger or height ofcorrugation is lower compared to typical corrugations or completecorrugations. For example, a pitch therebetween is 2.0 mm or longer inincomplete flat corrugations or flat and incomplete corrugated portion,while that is 1.5 mm in typical or complete corrugations. Or height of acorrugation (distance between a peak and a valley of a corrugation) is1.0 mm or lower in the incomplete flat corrugations or the flat andincomplete corrugations, while that is 1.5 mm in the typical or completecorrugations.

[0029] According to the present invention based on that knowledge, acorrugated metal tube may be provided with an axially straight tubularor axially straight-walled portion on one axial or longitudinal endportion thereof so as to extend for minimum 10 mm axially from a lastswaged point or a swaged point of a most opposite axial or longitudinalside of a socket fitting. That is, a longitudinal distance between theopposite longitudinal end of the straight tubular portion and the swagedpoint of the most opposite longitudinal side of the socket fitting isminimum 10 mm.

[0030] As a corrugated metal tube is provided with a straight tubularportion on one axial end portion thereof so as to extend beyond aposition of about 7.0 mm behind a last swaged point or away in anopposite axial direction from a position of about 7.0 mm behind a lastswaged point where the corrugated metal tube is likely cracked orbroken, the corrugated metal tube is favorably prevented from fatiguecrack or break caused by repeated internal pressures, and therebyservice life of a hose having the corrugated metal tube may beeffectively prolonged. Here, an opposite longitudinal end of thestraight tubular portion is located or extends beyond a position about7.0 mm behind the last swaged portion.

[0031] According to the present invention, instead of extending thestraight tubular or straight-walled portion for a predetermined lengthbehind or rearwardly from the last swaged point, a corrugated metal tubemay be provided with pre-formed flat and incomplete corrugated portionso as to extend for minimum 10 mm axially beyond a last swaged point. Inthis case, the corrugated metal tube is also favorably restrained fromfatigue crack or break and thereby service life of a hose having thecorrugated metal tube may be also prolonged. Here, an oppositelongitudinal end of the flat and incomplete corrugated portion islocated or extends beyond a position about 7.0 mm behind the last swagedpoint.

[0032] It is confirmed that a corrugated metal tube specifically islikely cracked or broken at the above-stated portion or position whenswaging rate is minimum 20% at the last swaged point. Therefore, thepresent invention proves more effective when swaging rate is minimum 20%at the last swaged point.

[0033] The swaging rate is given by the following formula.

Swaging rate=(T₀−T₁)/T₀×100(%)

[0034] where T₀ is a thickness of a hose body before swaged, and T₁ is athickness of a swaged point of the hose body after swaged.

[0035] Now, the preferred embodiments of the present invention will bedescribed in detail with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036]FIG. 1(A) is a perspective view of a hose with corrugated metaltube as one embodiment according to the present invention.

[0037]FIG. 1(B) is a perspective view showing construction of the hosewith corrugated metal tube, including a cross-sectional view of arelevant part thereof.

[0038]FIG. 2 is a cross-sectional view of a relevant portion of the hosewith corrugated metal tube.

[0039]FIG. 3(A) is a cross-sectional view to explain concrete dimensionsof the hose with corrugated metal tube.

[0040]FIG. 3(B) is a cross-sectional view of a relevant portion of acomparative example hose given for confirmation of effect in the aboveembodiment according to the present invention.

[0041]FIG. 4(A) is a cross-sectional view of a relevant portion of ahose with corrugated metal tube as another embodiment according to thepresent invention.

[0042]FIG. 4(B) is a cross-sectional view of a relevant portion of ahose with corrugated metal tube as yet another embodiment according tothe present invention.

[0043]FIG. 4(C) is a cross-sectional view of a relevant portion of ahose with corrugated metal tube as further another embodiment accordingto the present invention.

[0044]FIG. 5 is a cross-sectional view of a relevant portion of a hosewith corrugated metal tube to be contrasted with the present invention.

[0045]FIG. 6 is an explanatory view showing deformation of a corrugatedmetal tube.

[0046]FIG. 7 is a view used to explain status of a reinforced layer ofthe hose with corrugated metal tube in FIG. 5 when the hose withcorrugated metal tube is subject to internal pressure.

[0047]FIG. 8(A) is a cross-sectional view of a relevant portion of ahose with corrugated metal tube of a type in FIG. 5 before a socketfitting is swaged.

[0048]FIG. 8(B) is a cross-sectional view of a relevant portion of ahose with corrugated metal tube of a type in FIG. 5 after the socketfitting is swaged, including an enlarged view showing a defect causedthereon.

DETAILED DESCRIPTIONS OF PREFERRED EMBODIMENTS

[0049] In FIGS. 1 and 2, a numeral reference 10 indicates a hose withcorrugated metal tube (hereinafter referred to as a hose) which ispreferably adapted for hydrogen or hydrogen gas conveying hose,refrigerant conveying hose for air conditioners, automobile fuelconveying hose or the like. A numeral reference 12 indicates a hosebody, a numeral reference 14 a metal connecting pipe fixed to the hosebody 12, and a numeral reference 16 a metallic socket fitting fittedonto or on an outer surface of the hose body 12 on one axial end portionthereof.

[0050] The socket fitting 16 is securely compressed or swaged radiallyinwardly to the hose body 12 and thereby the connecting pipe 14 is,along with the socket fitting 16, fixedly secured to one axial endportion of the hose body 12 so as to clamp one axial end portion thereoffrom a radial inside and a radial outside thereof.

[0051] As shown in FIG. 2, the socket fitting 16 is securely compressedor swaged radially inwardly to the hose body 12 on three axially spacedpoints thereof. In FIG. 2, P₁ indicates a first swaged point nearest oneaxial or longitudinal end of the hose body 12, P₂ a second swaged pointand P₃ a third or last swaged point of most opposite axial orlongitudinal side thereof.

[0052] The socket fitting 16 has a radially inwardly directedcollar-like portion 18 on one axial end thereof, while the connectingpipe 14 is formed with a fit-engagement groove 20 at a position axiallycorresponding to the collar-like portion 18 on a radially outer surfacethereof. The collar-like portion 18 or an inner end portion of thecollar-like portion 18 is fitted in and engaged with the fit-engagementgroove 20 by securely compressing or swaging the socket fitting 16radially inwardly to the hose body 12.

[0053] As understood from FIG. 2, the hose body 12 has multi-layerconstruction which includes a corrugated metal tube 22 as an innermostlayer. The multi-layer construction also includes an inner elastic layer24, a reinforced (reinforcing) layer 26 and an outer elastic layer 28which circumscribe an outer side of the corrugated metal tube 22. Eachof the layers is fixedly bonded in unitary relation to an adjacent layerinto a composite hose by vulcanizing or other manner.

[0054] In this embodiment, the inner elastic layer 24, the reinforcedlayer 26 of middle layer and the outer elastic layer 28 construct outerlayer circumscribing the corrugated metal tube 22.

[0055] And, in this embodiment, the reinforced layer 26 is constructedby braiding or weaving reinforcing filament members at a pre-determinedbraid angle in opposed angled relation with one another or in opposedangled relation with respect to an axial or longitudinal direction. Thereinforced layer 26 may be a fiber-reinforced layer or a wire-reinforcedlayer.

[0056] And the inner elastic layer 24 and the outer elastic layer 28 maybe made of elastic material such as rubber.

[0057] On the other hand, the corrugated metal tube 22 as an innermostlayer is formed with corrugations 30 for generally entire axial lengththereof, which provides the corrugated metal tube 22 with flexibility.

[0058] That is, although, in this embodiment, an innermost layer of thehose 10 is a metal tube, the hose 10 is provided entirely withflexibility, thanks to the corrugations 30 formed on the metal tube.

[0059] The corrugated metal tube 22 may be made of materials such assteel products including stainless steel, copper, copper alloy,aluminum, aluminum alloy, nickel, nickel alloy, titanium or titaniumalloy, and preferably may be made of stainless steel.

[0060] A wall thickness of the corrugated metal tube 22 may be from 20to 500 μm, preferably is minimum 50 μm in view of preventing defectssuch as pinholes and further in view of processing of the corrugations30 or the like, and maximum 300 μm in view of flexibility anddurability.

[0061] The corrugated metal tube 22 has an axially straight-walledportion or axially straight tubular portion 32 extending straight in anaxial direction on one axial end side or one axial end portion.

[0062] The corrugated metal tube 22 or the straight tubular portion 32is configured as an extending portion 34 on a leading end side or oneaxial end side, which extends outwardly in an axial direction and isexposed out of the outer layer comprising the inner elastic layer 24,the reinforced layer 26 and the outer elastic layer 28.

[0063] And, the extending portion 34 is clamped radially with an innerend portion of the collar-like portion 18 and the fit-engagement groove20 of the connecting pipe 14 by securely compressing or swaging thesocket fitting 16. The corrugated metal tube 22 is firmly fixed to theconnecting pipe 14 at the fit-engagement groove 20, while an air tightseal is provided between the corrugated metal tube 22 and an outersurface of the connecting pipe 14.

[0064] Securing structure between an axial end portion or one axial endportion of the corrugated metal tube 22 and the connecting pipe 14 asstated is only one of embodiments. According to a shape of a connectingpipe 14 or other factors, securing structure and sealing structure maybe constructed in various manners between an axial end portion of acorrugated metal tube and a connecting pipe, for example, of variousshape.

[0065] In the embodiment shown in FIG. 2, the connecting pipe 14 and thestraight tubular portion 32 of the corrugated metal tube 22 are arrangedor formed respectively so as to extend for a distance L(L=15 mm in thisembodiment) longitudinally toward the right-hand side in FIG. 2 beyondthe third or last swaged point P₃ of the socket fitting 16, namely in adirection away from an axial end or one axial end of the hose body 12 orrearwardly. That is, an opposite longitudinal or axial end of thestraight tubular portion 32 is located or extends for the distance Ltoward an opposite longitudinal or axial side from the third or lastswaged point P₃.

[0066] And, in this embodiment, the socket fitting 16 or a cylindricalportion thereof is arranged or formed so as to extend further for adistance Q beyond opposite axial ends (right-hand ends or rear ends inFIG. 2) of the connecting pipe 14 and the straight tubular portion 32.

[0067] In the hose 10 of this embodiment, the corrugated metal tube 22is formed with the straight tubular portion 32 on one axial end portionthereof which is arranged so as to extend for a distance L beyond thethird or last swaged point P₃. That means, the straight tubular portion32 extends axially long beyond a position of about 7.0 mm behind thethird swaged point. P₃ where the corrugated metal tube 22 is most likelycracked or broken, thereby the corrugated metal tube 22 may be favorablyprevented from fatigue crack caused by repeated internal pressures, andservice life of the hose 10 may be effectively prolonged.

[0068] By the way, Table 1 shows results of Impulse Test (repeatedlypressurizing test) conducted on the hose 10 or sample according to thisembodiment and a comparative example hose with corrugated metal tube orcomparative example. In Table 1, for example, as for the hose 10 of theembodiment, the row No. 1 where a number of cycle repetitions is 31,000times and a cracking point is 17 mm means that the corrugated metal tubeof the hose of the embodiment is cracked or broken at 17 mm behind theswaged point P₃ when pressure is repeatedly exerted thereto 31,000times. TABLE 1 Results of Impulse Test Hose with Corrugated MetalComparative Example Hose with Tube of the Embodiment Corrugated MetalTube Cycle Repetitions Cracking Cycle Repetitions Cracking No. (10,000times) Point (mm) (10,000 times) Point (mm) 1 3.1 17.0 1.2 7.0 2 3.317.0 1.3 7.0 3 3.8 15.5 1.2 7.0 4 2.5 18.5 0.9 5.5 5 4.0 17.0 1.5 7.0 65.1 17.0 1.8 8.5 7 2.8 18.5 1.2 8.5 8 4.0 17.0 1.1 7.0 9 3.3 15.5 1.57.0 10 4.2 17.0 0.7 7.0

[0069] The hose of the embodiment or sample in Table 1 is shown in FIG.3(A). In this hose 10, the first swaged point P₁ is arranged at adistance La(La=8.0 mm) from an inner surface of the collar-like portion18, the second swaged point P₂ at a distance Lb(Lb=10 mm) from the firstswaged point P₁, and the third swaged point P₃ at a distance Lc(Lc=10mm) from the second swaged point P₂.

[0070] The straight tubular portion 32 and the connecting pipe 14 arearranged so as to extend for a distance L(L=15 mm) beyond the last orthird swaged point P₃ in a right-hand direction in FIG. 3(A).

[0071] The corrugated metal tube 22 is made of stainless steel (SUS) inthickness of 0.15 mm. The inner elastic layer 24 is made ofethylene-propylene-diene-rubber (EPDM) in thickness of 0.5 mm, while theouter elastic layer 28 is made also of EPDM in thickness of 1.0 mm.

[0072] The reinforced layer 26 is constructing by braiding reinforcingfilament member or members, or reinforcing threads, more specifically bybraiding aramid type triple-yarns of 1,500 D (deniers) with yarn countof 24 at braid angle 55°.

[0073] The corrugation 30 of the corrugated metal tube 22 is formed ofan inner diameter (full diameter) of 6.0 mm and an outer diameter (fulldiameter) of 9.0 mm.

[0074] On the first and the second swaged points P₁, P₂, the socketfitting 16 are swaged at swaging rate 30% respectively, while on thethird swaged point P₃ the socket fitting 16 is swaged at swaging rate20%.

[0075] The comparative example hose with corrugated metal tube orcomparative example in Table 1, which is of a type shown in FIG. 5, isshown in FIG. 3(B). This comparative example hose has basically similarconfiguration to the hose 10 of FIG. 3(A). However, in the comparativeexample hose, opposite axial or longitudinal ends (right-hand ends inFIG. 3(B)) of the connecting pipe 212 and the straight tubular portion201 of the corrugated metal tube 202 are arranged at a position axiallycorresponding to the last or third swaged point P₃.

[0076] And an opposite axial or longitudinal end (right-hand end in FIG.3(B)) of the socket fitting 210 is located at a distance Ld(Ld=4.0 mm)from the third swaged point P₃ toward an opposite axial or longitudinaldirection.

[0077] The impulse test is performed under conditions generallyaccording to JASO M321 specified by Japanese Automobile StandardsOrganization (JASO).

[0078] However, test pressures 0<-->10 Mpa are applied in this test,although test pressures 0<-->3.53 Mpa are specified in JASO M321.

[0079] As seen from the results of Table 1, cracking points on thecorrugated metal tubes 22, 202 differ between the hose 10 of theembodiment and the comparative example hose. And, thereby the hose 10 ofthe embodiment has longer duration life or service life.

[0080] As stated, the corrugated metal tube 22 of the hose 10 of theembodiment is broken at points different from those of the corrugatedmetal tube 202 of the comparative example hose, and the hose 10 of theembodiment has longer duration life than the comparative example hose.In the hose 10 of the embodiment, the straight tubular portion 32 on oneaxial end portion of the corrugated metal tube 22 extends long beyondpossible breaking points in the comparative example hose, and there isno or little loosen or irregular portion in the reinforced layer 26 evenunder compressing or swaging pressure at an axial position adjacent tothe straight tubular portion 32. It is estimated that these factorscooperate each other to realize long duration life of the hose 10.

[0081] Table 2 shows elongation of the hose body 12 of the hose 10 at 0to 5 mm, 5 to 10 mm, 10 to 15 mm and beyond 15 mm from the swaged pointP₃ under various swaged rates at the third swaged point P₃, wheninternal pressure 10 Mpa is exerted thereto.

[0082] In Table 2, “Main Part of the Hose” means a portion of the hosebody 12 beyond 15 mm from the swaged portion P₃. TABLE 2 Swaging Rate(%) Swaged Point P1 30 30 30 P2 30 30 30 P3 30 20 10 Elongation Distance 0 to 5 mm 0.8 0.6 0.4 under from the  5 to 10 mm 0.5 0.4 0.3 PressureSwaged 10 to 15 mm 0.3 0.2 0.2 10 Mpa Point P₃ (mm) Main Part of theHose 0.13 0.13 0.13 (beyond 15 mm)

[0083] Table 2 shows that the hose body 12 of the hose 10 of thisembodiment elongates largely or at high rate in the range of 10 mm fromthe third swaged point P₃ while elongates a little or at low rate beyondthat range specifically in case that the swaging rate is 20% or higherat the third swaged point P₃. Elongation of the hose body 12 variesdepending on swaging rate at the third swaged point P₃. When the swagingrate at the third swaged point P₃ is under 20%, elongation thereofbecomes a little or at low rate, even in the distance from the swagedpoint P₃ of “5 to 10 mm”.

[0084] In other words, the reinforced layer 26 tends to be loosenlargely or at high rate in the range of 10 mm from the third swagedpoint P₃ specifically in case that the swaging rate is 20% or higher atthe third swaged point P₃, and loosening degree varies depending onswaging rate.

[0085] The above is only one embodiment of the present invention.According to the present invention, a hose with corrugated metal tubemay be constructed in variety of modes.

[0086]FIG. 4(A) shows another embodiment of the present invention. Inthe another embodiment, a straight tubular portion 32 of a corrugatedmetal tube 22 is formed so as to extend further rearwardly (right-handside in FIG. 4(A)) compared to that of the first embodiment shown inFIG. 2, namely so as to extend for a distance L₁ (L₁>L) behind orrearwardly from a third swaged point P₃.

[0087]FIG. 4(B) shows yet another embodiment of the present invention.In the yet another embodiment of the present invention, only a straighttubular portion 32 is formed so as to extend for a distance L behind orrearwardly from a third swaged point P₃, while a connecting pipe 14 isformed so that an opposite axial or longitudinal end (right-hand end inFIG. 4(B)) thereof extends to a position axially corresponding to thethird swaged point P₃.

[0088] According to the present invention, a swaged point located mostfar away from one axial end of a hose body 12 or in most opposite axialside of points which are swaged at minimum 20% may be determined as lastswaged point and a hose 10 may be constructed by forming a straighttubular portion 32 so as to extend for minimum 10 mm from this lastswaged point.

[0089]FIG. 4(C) shows thus constructed hose 10 as further anotherembodiment.

[0090] In the further another embodiment, a socket fitting 16 iscompressed or swaged radially inwardly to the hose body 12 also at aforth swaged point P₄ further behind or rearwardly from the third swagedpoint P₃ in a hose of a type of the first embodiment.

[0091] However, the swaging rate at the forth swaged point P₄ is under20% while the swaging rate at swaged points P₁, P₂, P₃ is minimum 20% inthe first to forth embodiments shown in FIGS. 1 , 2, 4(A), 4(B) and4(C). In the further another embodiment, the straight tubular portion 32of the corrugated metal tube 22 extends for a distance L (L is minimum10 mm) from the third swaged point P₃ and terminates ahead of the forthswaged point P4 or on one axial or longitudinal side from the forthswaged point P₄.

[0092] In the above embodiments, the straight tubular portion 32 isformed so as to extend relatively long. However, instead, pre-formedflat and incomplete corrugations may be arranged so as to extend forminimum 10 mm beyond the third swaged point P₃. Here, an oppositelongitudinal or axial end of the pre-formed flat and incompletecorrugations is located or extends for minimum 10 mm behind the thirdswaged point P₃. In this configuration, also the corrugated metal tube22 may be favorably prevented from fatigue crack and duration, andservice life of the hose 10 may be prolonged.

[0093] Although the present invention has been described in terms ofpreferred embodiments, it will be understood that a variety ofmodifications can be made without departing from the spirit and thescope of the invention.

We claim:
 1. A hose with corrugated metal tube, comprising: a hose bodyhaving inner layer including a corrugated metal tube and outer layerincluding reinforced layer and circumscribing a radial outer side of theinner layer, the corrugated metal tube being provided with a straighttubular portion extending straight in a longitudinal direction and/or aflat and incomplete corrugated portion on one longitudinal end portionthereof; a socket fitting fitted on the hose body at one longitudinalend portion thereof, and compressed or swaged radially inwardly to besecured thereto; an opposite longitudinal end of the straight tubularportion or the flat and incomplete corrugated portion being locatedtoward an opposite longitudinal side from a compressed or swaged pointof a most opposite longitudinal side of the socket fitting; and alongitudinal distance between the opposite longitudinal end of thestraight tubular portion or the flat and incomplete corrugated portionand the compressed or swaged point of the most opposite longitudinalside of the socket fitting being minimum 10 mm.
 2. The hose withcorrugated metal tube as set forth in claim 1 wherein a compressing orswaging rate for the socket fitting at the compressed or swaged point ofthe most opposite longitudinal side of the socket fitting is minimum20%.